Epitaxial Heterostructures of Ultrathin Topological Insulator Nanoplate and Graphene

The authors present a van der Waals epitaxy of high-quality ultrathin nanoplates of topological insulator Bi2Se3 on a pristine graphene substrate using a simple vapor-phase deposition method. Sub-10-nm-thick nanoplates of layered Bi2Se3 with defined orientations can be epitaxially grown on a few-layer pristine graphene substrate. We show the evolution of Raman spectra with the number of Bi2Se3 layers on few-layer graphene. Bi2Se3 nanoplates with a thickness of three quintuple-layers (3-QL) exhibit the strongest Raman intensity. Strain effects in the Bi2Se3/graphene nanoplate heterostructures is also studied by Raman spectroscopy. 1-QL and 2-QL Bi2Se3 nanoplates experience tensile stress, consistent with compressive stress in single-layer and bilayer graphene substrates. Our results suggest an approach for the synthesis of epitaxial heterostructures that consist of an ultrathin topological insulator and graphene, which may be a new direction for electronic and spintronic applications.